Hydrogen which is a material having most light and simple structure on earth has physical and chemical characteristic of about 6 times of laminar flame velocity and about three times of lower heating value compared with gasoline. Accordingly, during combusting by properly mixing gasoline and hydrogen, combustion speed and combustion stability may be increased to improve thermal efficiency by expanding lean boundary or increasing supply amount of exhaust gas recirculation.
Meanwhile, a fuel reformer is a system generating hydrogen. The hydrogen is generated by reacting separate gasoline fuel supplied to the reformer with a catalyst in the reformer using thermal energy of high temperature exhaust gas exhausted from an engine.
By the way, in a certain driving condition that the exhaust gas temperature is high, cooling the fuel reformer is necessary to prevent an injector in the fuel reformer from being overheated. For this, in a conventional technology, structure of the fuel reforming system is complicated and system cost and weight increases. Also, efficiency of the fuel reformer is influenced by temperature of catalyst in the fuel reformer, therefore means to control the coolant supplied to the fuel reformer for improving reforming efficiency in various driving conditions.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.